A radio communication system in which base stations having a cell radius as small as around 10 m, named Femto base stations, are arranged has recently been implemented so as to allow for radio communication in a poor reception area.
However, if Femto base stations are arranged as base stations, since the cell radius of each Femto base stations is small, they need to be densely arranged. If they are arranged in such a manner, base stations adversely interfere with neighboring base stations.
As a method that decreases interference between base stations, Patent Literature 1 discloses a technique in which the system side measures the interference of channels and assigns small interference frequencies to base stations.
As another method that decreases interference between base stations, Patent Literature 2 discloses a technique in which a base station receives information about spread codes that neighboring base stations use from a highly hierarchical station and selects a spread code other than those that the neighboring base stations use, namely a small interference spread code.